Method and device for transmitting and receiving control information in wireless cellular communication system

ABSTRACT

The present disclosure relates to a communication technique for combining IoT technology with a 5G communication system for supporting a higher data transmission rate than 4G communication systems, and a system therefor. The present disclosure may be applied to intelligent services (e.g., smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail, security- and safety-related services, etc.) on the basis of 5G communication technology and IoT-related technology. The present disclosure relates to a method and device for transmitting and receiving control information.

PRIORITY

This application is a National Phase Entry of PCT InternationalApplication No. PCT/KR2019/005175 which was filed on Apr. 30, 2019, andclaims priority to Korean Patent Application No. 10-2018-0054223, whichwas filed on May 11, 2018, the content of each of which is incorporatedherein by reference.

TECHNICAL FIELD

The disclosure relates to a wireless communication system and, moreparticularly, to a method and apparatus for smoothly providing a servicein a communication system. More specifically, the disclosure relates toa method and apparatus for transmitting or receiving control informationby a terminal in a communication system.

BACKGROUND ART

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a “Beyond 4G Network” or a“Post LTE System”.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, coordinated multi-points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, hybrid FSK and QAM modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess(NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have also been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofeverything (IoE), which is a combination of the IoT technology and thebig data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “security technology” have been demanded forIoT implementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing information technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, machine type communication (MTC), andmachine-to-machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud radioaccess network (RAN) as the above-described big data processingtechnology may also be considered an example of convergence of the 5Gtechnology with the IoT technology.

As described above, a plurality of services can be provided to a user ina communication system, and in order to provide the plurality ofservices to the user, a method capable of providing respective servicesaccording to characteristics in the same time section and an apparatususing the same are required. Various services provided in the 5Gcommunication system are being studied, and one criterion for suchservices is a service that satisfies a low-latency requirement. Anotherone is that the services satisfy a high-reliability requirement.Consideration of both of these requirements is described in thedisclosure as ultra-reliability and low latency communication (URLLC).In order to dynamically support a service that satisfies various URLLCrequirements, a base station needs a method of dynamically supportingvarious methods of performing transmission to a terminal.

DISCLOSURE OF INVENTION Technical Problem

An embodiment of the specification has been proposed in order to solvethe above-mentioned problems, and aims to provide a method and anapparatus for simultaneously providing different types (or the sametype) of services. In addition, an embodiment of the specification is toprovide various methods and apparatuses for determining a modulation andcoding scheme (MCS) by a terminal. In addition, an embodiment of thespecification is to provide a method and apparatus for supportingmultiple modulation and coding schemes (MCS) by a base station.Specifically, an embodiment is to provide a method for indicating orconfiguring, by a base station, a specific MCS table for a terminal in asituation where the terminal receives support according to two or moreMCS tables.

Solution to Problem

In order to solve the above problems, a method by a terminal accordingto an embodiment includes: receiving, from a base station, downlinkcontrol information (DCI) for scheduling a physical downlink sharedchannel (PDSCH) or a physical uplink shared channel (PUSCH); identifyinga radio network temporary identifier (RNTI) scrambled in a cyclicredundancy check (CRC) of the DCI; and if the CRC of the DCI isscrambled by an RNTI associated with a modulation and coding scheme(MCS) table, determining a modulation order and a target code rate to beused for the PDSCH or the PUSCH, based on a first MCS table associatedwith the RNTI.

In order to solve the above problems, a method by a base stationaccording to an embodiment includes: generating downlink controlinformation (DCI) for scheduling a physical downlink shared channel(PDSCH) or a physical uplink shared channel (PUSCH); scrambling a cyclicredundancy check (CRC) of the DCI using a radio network temporaryidentifier (RNTI), which is identified based on a modulation order and atarget code rate to be used for the PDSCH or the PUSCH; and transmittingthe DCI to a terminal, wherein, if the CRC of the DCI is scrambled by anRNTI associated with a modulation and coding scheme (MCS) table, themodulation order and the target code rate are determined based on afirst MCS table associated with the RNTI.

In order to solve the above problems, a terminal according to anembodiment includes: a transceiver configured to transmit or receive asignal; and a controller configured to receive, from a base station,downlink control information (DCI) for scheduling a physical downlinkshared channel (PDSCH) or a physical uplink shared channel (PUSCH),identify a radio network temporary identifier (RNTI) scrambled in acyclic redundancy check (CRC) of the DCI, and if the CRC of the DCI isscrambled by an RNTI associated with a modulation and coding scheme(MCS) table, determine a modulation order and a target code rate to beused for the PDSCH or the PUSCH, based on a first MCS table associatedwith the RNTI.

In order to solve the above problems, a base station according to anembodiment includes: a transceiver configured to transmit or receive asignal; and a controller configured to generate downlink controlinformation (DCI) for scheduling a physical downlink shared channel(PDSCH) or a physical uplink shared channel (PUSCH), scramble a cyclicredundancy check (CRC) of the DCI using a radio network temporaryidentifier (RNTI), which is identified based on a modulation order and atarget code rate to be used for the PDSCH or the PUSCH, and transmit theDCI to a terminal, wherein, if the CRC of the DCI is scrambled by anRNTI associated with a modulation and coding scheme (MCS) table, themodulation order and the target code rate are determined based on afirst MCS table associated with the RNTI.

Advantageous Effects of Invention

According to the current embodiment, a base station in a communicationsystem supports various services having different latency andreliability requirements for different respective terminals. Inaddition, according to another embodiment, it is possible for a terminalto receive support of various modulation and coding schemes in acommunication system.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a downlink time-frequency domain transmissionstructure of a long-term evolution (LTE) or LTE advanced (LTE-A) system;

FIG. 2 illustrates an uplink time-frequency domain transmissionstructure of an LTE or LTE-A system;

FIG. 3 is a flowchart illustrating a method for determining an MCS tableby a terminal according to a first embodiment;

FIG. 4 is a flowchart illustrating a method for determining an MCS tableby a terminal according to a second embodiment;

FIG. 5 is a flowchart illustrating a method for determining an MCS tableby a terminal according to a third embodiment;

FIG. 6 is a flowchart illustrating a method for determining an MCS tableby a terminal according to a fourth embodiment;

FIG. 7 is a flowchart illustrating a method for determining an MCS tableby a terminal according to a fifth embodiment;

FIG. 8 is a flowchart illustrating a method for determining an MCS tableby a terminal according to a sixth embodiment;

FIG. 9 is a flowchart illustrating a method for determining an MCS tableby a terminal according to a seventh embodiment;

FIG. 10 is a flowchart illustrating a method for determining an MCStable by a terminal according to an eighth embodiment;

FIG. 11 is a flowchart illustrating a method for determining an MCStable by a terminal according to a ninth embodiment;

FIG. 12 is a block diagram illustrating the structure of a terminalaccording to embodiments; and

FIG. 13 is a block diagram illustrating the structure of a base stationaccording to embodiments.

MODE FOR THE INVENTION

Hereinafter, embodiments of the disclosure will be described in detailwith reference to the accompanying drawings.

In describing embodiments of the disclosure, descriptions related totechnical contents well-known in the art and not associated directlywith the disclosure will be omitted. Such an omission of unnecessarydescriptions is intended to prevent obscuring of the main idea of thedisclosure and more clearly transfer the main idea.

For the same reason, in the accompanying drawings, some elements may beexaggerated, omitted, or schematically illustrated. Further, the size ofeach element does not completely reflect the actual size. In thedrawings, identical or corresponding elements are provided withidentical reference numerals.

The advantages and features of the disclosure and ways to achieve themwill be apparent by making reference to embodiments as described belowin detail in conjunction with the accompanying drawings. However, thedisclosure is not limited to the embodiments set forth below, but may beimplemented in various different forms. The following embodiments areprovided only to completely disclose the disclosure and inform thoseskilled in the art of the scope of the disclosure, and the disclosure isdefined only by the scope of the appended claims. Throughout thespecification, the same or like reference numerals designate the same orlike elements.

Here, it will be understood that each block of the flowchartillustrations, and combinations of blocks in the flowchartillustrations, can be implemented by computer program instructions.These computer program instructions can be provided to a processor of ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions specified in the flowchart block or blocks.These computer program instructions may also be stored in a computerusable or computer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer usable orcomputer-readable memory produce an article of manufacture includinginstruction means that implement the function specified in the flowchartblock or blocks. The computer program instructions may also be loadedonto a computer or other programmable data processing apparatus to causea series of operational steps to be performed on the computer or otherprogrammable apparatus to produce a computer implemented process suchthat the instructions that execute on the computer or other programmableapparatus provide steps for implementing the functions specified in theflowchart block or blocks.

Further, each block of the flowchart illustrations may represent amodule, segment, or portion of code, which includes one or moreexecutable instructions for implementing the specified logicalfunction(s). It should also be noted that in some alternativeimplementations, the functions noted in the blocks may occur out of theorder. For example, two blocks shown in succession may in fact beexecuted substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved.

As used herein, the “unit” refers to a software element or a hardwareelement, such as a Field Programmable Gate Array (FPGA) or anApplication Specific Integrated Circuit (ASIC), which performs apredetermined function. However, the “unit” does not always have ameaning limited to software or hardware. The “unit” may be constructedeither to be stored in an addressable storage medium or to execute oneor more processors. Therefore, the “unit” includes, for example,software elements, object-oriented software elements, class elements ortask elements, processes, functions, properties, procedures,sub-routines, segments of a program code, drivers, firmware,micro-codes, circuits, data, database, data structures, tables, arrays,and parameters. The elements and functions provided by the “unit” may beeither combined into a smaller number of elements, or a “unit”, ordivided into a larger number of elements, or a “unit”. Moreover, theelements and “units” or may be implemented to reproduce one or more CPUswithin a device or a security multimedia card. Further, the “unit” inthe embodiments may include one or more processors.

Wireless communication systems, which provided voice-oriented servicesin early stages, have evolved into broadband wireless communicationsystems that provide high-speed and high-quality packet data servicesaccording to communication standards such as high-speed packet access(HSPA) of 3GPP, long-term evolution (LTE), evolved universal terrestrialradio access (E-UTRA), LTE-advanced (LTE-A), high-rate packet data(HRPD) of 3GPP2, ultra-mobile broadband (UMB), and IEEE 802.16e. Inaddition, a communication standard of 5G or new radio or next radio (NR)is being produced as a 5^(th)-generation wireless communication system.

As described above, in a wireless communication system including a5^(th)-generation wireless communication system, at least one serviceamong enhanced mobile broadband (eMBB), massive machine-typecommunications (mMTC), and ultra-reliable and low-latency communications(URLLC) may be provided to a terminal. The services may be provided tothe same terminal during the same time period. In an embodiment, eMBBmay be a service aiming at high-speed transmission of high-capacitydata, mMTC may be a service aiming at minimization of terminal powerconsumption and access by multiple terminals, and URLLC may be a serviceaiming at high reliability and low latency, but the disclosure is notintended to be limited thereto. The three services may be a mainscenario in an LTE system or a system such as 5G and/or NR after the LTEsystem. According to an embodiment of the disclosure, a method forcoexistence between eMBB and URLLC or coexistence between mMTC andURLLC, and an apparatus using the same are described.

If a base station has scheduled, for any terminal, data corresponding toan eMBB service during a particular transmission time interval (TTI), ifthere occurs the situation where URLLC data must be transmitted duringthe TTI, a part of the eMBB data may not be transmitted in a frequencyband in which the eMBB data is already scheduled and transmitted, butthe generated URLLC data may be transmitted in the frequency band. Theterminal for which the eMBB data has been scheduled and the terminal forwhich the URLLC data has been scheduled may be the same terminal ordifferent terminals. In the example, since there occurs the situationwhere a part of the eMBB data that has already been scheduled fortransmission is not actually transmitted, the possibility that the eMBBdata will be damaged becomes higher. Accordingly, in the above case, itis necessary to determine a method for processing a received signal bythe terminal for which the eMBB data has been scheduled or by theterminal for which the URLLC data has been scheduled, or a signalreception method thereof.

Therefore, according to an embodiment of the disclosure, a descriptionis provided of a method for coexistence of heterogeneous services forenabling transmission of information according to each service when partor all of a frequency band is shared so as to schedule pieces ofinformation (which may include data and control information) accordingto eMBB and URLLC, simultaneously schedule pieces of informationaccording to mMTC and URLLC, simultaneously schedule pieces ofinformation according to mMTC and eMBB, or simultaneously schedulepieces of information according to eMBB, URLLC, and mMTC.

Hereinafter, embodiments of the disclosure will be described in detailwith reference to the accompanying drawings. In addition, in describingthe disclosure, if it is determined that a detailed description ofrelated functions or configurations may unnecessarily obscure thesubject matter of the disclosure, the detailed description will beomitted. In addition, terms to be described later are terms defined inconsideration of functions in the disclosure, and may vary according toa user's or operator's intention or practice. Therefore, the definitionshould be made based on the contents throughout this specification.

Hereinafter, a base station is the entity that performs resourceallocation for a terminal, and may be at least one of a gNode B, aneNode B, a Node B, a base station (BS), a radio access unit, a basestation controller, or a node on a network. A terminal may include auser equipment (UE), a mobile station (MS), a terminal, a cellularphone, a smart phone, a computer, or a multimedia system capable ofperforming communication functions. In the disclosure, a downlink (DL)indicates a radio transmission path of a signal transmitted by a basestation to a terminal, and an uplink (UL) indicates a radio transmissionpath of a signal transmitted by the terminal to the base station. Inaddition, although an embodiment of the disclosure is described below asan example of an LTE or LTE-A system, the embodiment of the disclosuremay be applied to other communication systems having a similar technicalbackground or channel form. For example, 5G mobile communicationtechnology, developed after LTE-A, may be included in othercommunication systems. In addition, the embodiments of the disclosuremay be applied to other communication systems through some modificationswithin a range that does not significantly depart from the scope of thedisclosure, according to the determination of those skilled in the art.

As a representative example of broadband wireless communication systems,an LTE system (hereinafter, examples of the LTE system may include LTEand LTE-A systems) adopts an orthogonal frequency division multiplexing(OFDM) scheme in a downlink, and adopts a single carrier frequencydivision multiple access (SC-FDMA) scheme in an uplink. The term“uplink” refers to a radio link through which a terminal transmits dataor a control signal to a base station, and the term “downlink” refers toa radio link through which a base station transmits data or a controlsignal to a terminal. The above-described multiple access schemenormally allocates and operates time-frequency resources, which carrydata or control information to be transmitted according to users, so asto prevent the time-frequency resources from overlapping each other,that is, establish orthogonality, thus making it possible to distinguishthe data or control information of one user from another.

If a decoding failure occurs upon initial transmission, the LTE systemadopts a hybrid automatic repeat request (HARQ) scheme forretransmitting the relevant data in a physical layer. If a receiverfails to accurately decode data, the HARQ scheme enables the receiver totransmit, to a transmitter, information (negative acknowledgement(NACK)) providing notification of the decoding failure and thus thetransmitter can retransmit the corresponding data in the physical layer.The receiver combines the data retransmitted by the transmitter with thedata for which decoding failed, thereby increasing the data receptionperformance. In addition, if the receiver accurately decodes the data,information (acknowledgement (ACK)) providing notification of decodingsuccess is transmitted to the transmitter, and thus the transmitter maytransmit new data.

FIG. 1 illustrates the basic structure of a time-frequency domain, thatis, a radio resource domain, in which data or control information istransmitted in a downlink of an LTE system and a system similar thereto.

Referring to FIG. 1, the horizontal axis represents the time domain andthe vertical axis represents the frequency domain. A minimumtransmission unit in the time domain is an OFDM symbol, in which oneslot 106 is configured by collecting N_(symb) OFDM symbols 102 and onesubframe 105 is configured by collecting two slots. The length of eachslot is 0.5 ms and the length of each subframe is 1.0 ms. In addition, aradio frame 114 is a time domain unit which includes 10 subframes. Theminimum transmission unit in the frequency domain is a subcarrier, inwhich the entire system transmission bandwidth includes a total ofN_(BW) subcarriers 104. In this configuration, the specific values maybe variably applied.

The basic unit of resources in the time-frequency domain is a resourceelement (RE) 112, and may be represented by an OFDM symbol index and asubcarrier index. A resource block (RB) (or a physical resource block(PRB)) 108 may be defined by N_(symb) consecutive OFDM symbols 102 inthe time domain and N_(RB) consecutive subcarriers 110 in the frequencydomain. Accordingly, in one slot, one RB 108 may include N_(symb)×N_(RB)REs 122. Generally, the minimum allocation unit of data in the frequencydomain is the RB unit. In the LTE system, generally, N_(symb)=7 andN_(RB)=12, and N_(BW) may be proportional to the bandwidth of the systemtransmission band. The data rate is increased in proportion to thenumber of RBs scheduled for the terminal. The LTE system may define andoperate six transmission bandwidths. In an FDD system, which operatesthe downlink and the uplink separated in the frequency domain, adownlink transmission bandwidth and an uplink transmission bandwidth maybe different from each other. The channel bandwidth represents a radiofrequency (RF) bandwidth, which corresponds to the system transmissionbandwidth. <Table 1> below shows the correspondence relationship betweenthe system transmission bandwidth and channel bandwidth defined in theLTE system. For example, in an LTE system having a channel bandwidth of10 MHz, a transmission bandwidth may include 50 RBs.

TABLE 1 Channel bandwidth 1.4 3 5 10 15 20 BW_Channel [MHz] Transmissionbandwidth 6 15 25 50 75 100 configuration N_RB

Downlink control information may be transmitted within the first N OFDMsymbols within the subframe. In an embodiment, generally, N={1, 2, 3}.Accordingly, the value of N may be variably applied to each subframedepending on the amount of control information that needs to betransmitted in the current subframe. The control information to betransmitted may include a control channel transmission sectionindicator, indicating the number of OFDM symbols in which the controlinformation is transmitted, scheduling information for downlink data oruplink data, and information for HARQ ACK/NACK.

In the LTE system, scheduling information of downlink data or uplinkdata is delivered from a base station to a terminal through downlinkcontrol information (DCI). The DCI may be defined depending on variousformats. According to each format, the DCI may indicate whether the DCIis scheduling information (UL grant) of the uplink data or schedulinginformation (DL grant) of the downlink data, whether the DCI is compactDCI having small-sized control information, whether to apply spatialmultiplexing using multiple antennas, whether the DCI is DCI for powercontrol, and the like. For example, DCI format 1, which is thescheduling control information (DL grant) of the downlink data, mayinclude at least one piece of information among the following pieces ofcontrol information.

-   -   Resource allocation type 0/1 flag: indicates whether a resource        allocation scheme is type 0 or type 1. Type 0 applies a bitmap        scheme so as to allocate resources in units of resource block        groups (RBGs). In the LTE system, the basic unit of scheduling        is an RB, represented by a time-frequency domain resource, and        an RBG includes multiple RBs, and thus becomes a basic unit of        scheduling in the type 0 scheme. Type 1 allocates a certain RB        within an RBG.    -   Resource block assignment: indicates an RB allocated to data        transmission. The represented resource is determined according        to the system bandwidth and a resource allocation scheme.    -   Modulation and coding scheme (MCS): indicates the modulation        scheme used for data transmission and the size of a transport        block (TB), that is, the data to be transmitted.    -   HARQ process number: indicates a HARQ process number.    -   New data indicator: indicates a HARQ initial transmission or        retransmission.    -   Redundancy version: indicates the redundancy version of data to        be transmitted during transmission according to HARQ.    -   Transmit power control (TPC) command for physical uplink control        channel (PUCCH): indicates a transmit power control command for        a PUCCH, which is an uplink control channel.

The DCI may be subjected to a channel coding and modulation process, andmay then be transmitted through a physical downlink control channel(PDCCH) (or downlink control information transmitted through a PDCCH,the terms “PDCCH” and “downlink control information” beinginterchangeably used hereinafter) or an enhanced PDCCH (EPDCCH) (ordownlink control information transmitted through an EPDCCH, “EPDCCH” and“downlink control information” being interchangeably used hereinafter).

Generally, the DCI is independently scrambled by a particular radionetwork temporary identifier (RNTI) (which may be understood as aterminal identifier or a terminal ID) for each terminal so as to have acyclic redundant check (CRC) bit added thereto, is channel-coded, and isthen configured as independent PDCCH and then transmitted. In the timedomain, the PDCCH is mapped and then transmitted during the controlchannel transmission section. The mapping location in the frequencydomain of the PDCCH may be determined based on an identifier of eachterminal and transmitted over the entire system transmission bandwidth.

The downlink data may be transmitted through a physical downlink sharedchannel (PDSCH), which is a physical channel for downlink datatransmission. The PDSCH may be transmitted after the control channeltransmission section in the time axis, and scheduling information of adetailed mapping location in the frequency domain of the PDSCH, amodulation scheme, or the like may be determined based on the DCItransmitted through the PDCCH.

Through MCS, among the pieces of control information configuring theDCI, a base station provides notification of the modulation schemeapplied to a PDSCH to be transmitted to a terminal and the size of data(transport block size (TBS)) to be transmitted. In an embodiment, theMCS may include 5 bits or a number of bits greater than or less than 5bits. The TBS corresponds to a size before channel coding for errorcorrection is applied to a data transport block (TB) to be transmittedby the base station.

Modulation schemes supported by the LTE system include quadrature phaseshift keying (QPSK), 16 quadrature amplitude modulation (QAM), and 64QAM, of which modulation orders Qms correspond to 2, 4, and 6,respectively. That is, in the case of QPSK modulation, 2 bits per symbolmay be transmitted, in the case of 16 QAM modulation, 4 bits per symbolmay be transmitted, and in the case of 64 QAM modulation, 6 bits persymbol may be transmitted. In addition, modulation schemes above 256 QAMmay be used depending on system modification.

FIG. 2 illustrates a basic structure of a time-frequency domain, thatis, a radio resource domain, in which data or control information istransmitted in an uplink of an LTE system and a system similar thereto.

Referring to FIG. 2, the horizontal axis represents the time domain andthe vertical axis represents the frequency domain. The minimumtransmission unit in the time domain is an SC-FDMA symbol, and one slot206 may be configured by collecting N_(symb) SC-FDMA symbols 202. Inaddition, one subframe 205 is configured by collecting two slots. Oneradio frame 214 is configured by collecting 10 subframes. The minimumtransmission unit in the frequency domain is a subcarrier, in which anentire system transmission bandwidth 204 includes a total of N_(BW)subcarriers 204. N_(BW) may have a value proportional to the systemtransmission bandwidth.

The basic unit of resources in the time-frequency domain is a resourceelement (RE) 212, and may be defined by an SC-FDMA symbol index and asubcarrier index. A resource block (RB) 208 may be defined by N_(symb)consecutive SC-FDMA symbols in the time domain and N_(RB) consecutivesubcarriers 210 in the frequency domain. Accordingly, one RB includesN_(symb)×N_(RB) REs. In general, a minimum transmission unit of data orcontrol information is an RB unit. A PUCCH is mapped to a frequencydomain corresponding to one RB and transmitted in one subframe.

In the LTE system, it is possible to define a timing relationship of aPUCCH or a PUSCH, that is, an uplink physical channel, through which aHARQ ACK/NACK corresponding to a PDSCH as a physical channel fordownlink data transmission or a PDCCH or EPDDCH including asemi-persistent scheduling release (SPS release) is transmitted. Forexample, in an LTE system operating according to frequency divisionduplex (FDD), HARQ ACK/NACK, corresponding to the PDSCH transmitted inan (n-4)th subframe, or PDCCH or EPDCCH including the SPS release may betransmitted through the PUCCH or the PUSCH in an n-th subframe.

In the LTE system, a downlink HARQ adopts an asynchronous HARQ scheme inwhich a data retransmission time point is not fixed. That is, if, forinitial transmission data transmitted by the base station, the HARQ NACKis fed back from the terminal, the base station freely determines thetransmission time point of data to be retransmitted based on ascheduling operation. The terminal may perform buffering of data, whichis determined as an error as a result of decoding the received data fora HARQ operation, and may then combine the same with data to beretransmitted next.

If the terminal receives a PDSCH including downlink data transmittedfrom the base station in subframe n, the terminal transmits uplinkcontrol information including a HARQ ACK or a NACK of the downlink datato the base station through a PUCCH or PUSCH in subframe (n+k). Forexample, k may be defined differently depending on whether the LTEsystem adopts FDD or time division duplex (TDD), and the UL/DL subframeconfiguration thereof. For example, in the case of an FDD LTE system, kis fixed to 4. In the case of a TDD LTE system, k may be determinedaccording to a subframe configuration and a subframe number. Inaddition, if data is transmitted through multiple carriers, the value ofk may be applied differently depending on the TDD configuration of eachcarrier.

In the LTE system, unlike a downlink HARQ, an uplink HARQ adopts asynchronous HARQ scheme in which a data transmission time point isfixed. That is, an uplink/downlink timing relationship between aphysical uplink shared channel (PUSCH), which is a physical channel foruplink data transmission, a PDCCH, which is a downlink control channelpreceding the PUSCH, and a physical hybrid indicator channel (PHICH),which is a physical channel through which a downlink HARQ ACK/NACKcorresponding to the PUSCH is transmitted, may be determined by thefollowing rules.

If, in the subframe n, the terminal receives a PDCCH including uplinkscheduling control information transmitted from the base station or aPHICH through which a downlink HARQ ACK/NACK is transmitted, theterminal transmits uplink data corresponding to the control informationthrough a PUSCH in a sub frame (n+k). In this case, k may be defineddifferently depending on whether the LTE system adopts FDD or TDD, andon the subframe configuration thereof. For example, in the case of a FDDLTE system, k may be fixed to 4. In the case of a TDD LTE system, k maybe determined according to a subframe configuration and a subframenumber. In addition, if data is transmitted through multiple carriers,the value of k may be applied differently depending on the TDDconfiguration of each carrier.

In addition, if, in subframe i, the terminal receives a PHICH includinginformation related to the downlink HARQ ACK/NACK from the base station,the PHICH corresponds to a PUSCH that the terminal transmits in subframe(i-k). For example, k may be defined differently depending on whetherFDD or TDD is implemented in the LTE system and on the subframeconfiguration thereof. For example, in the case of the FDD LTE system, kis fixed to 4. In the case of the TDD LTE system, k may be determinedaccording to the subframe configuration and the subframe number. Inaddition, if data is transmitted through multiple carriers, the value ofk may be applied differently depending on the TDD configuration of eachcarrier.

TABLE 2 Transmission scheme of Transmission DCI PDSCH corresponding modeformat Search Space to PDCCH Mode 1 DCI Common and UE Single-antennaport, format 1A specific by port 0 (see subclause C-RNTI 7.1.1) DCI UEspecific by Single-antenna port, format 1 C-RNTI port 0 (see subclause7.1.1) Mode 2 DCI Common and UE Transmit diversity format 1A specific by(see subclause 7.1.2) C-RNTI DCI UE specific by Transmit diversityformat 1 C-RNTI (see subclause 7.1.2) Mode 3 DCI Common and UE Transmitdiversity format 1A specific by (see subclause 7.1.2) C-RNTI DCI UEspecific by Large delay CDD (see format 2A C-RNTI subclause 7.1.3) orTransmit diversity (see subclause 7.1.2) Mode 4 DCI Common and UETransmit diversity format 1A specific by (see subclause 7.1.2) C-RNTIDCI UE specific by Closed-loop spatial format 2 C-RNTI multiplexing (seesubclause 7.1.4) or Transmit diversity (see subclause 7.1.2) Mode 5 DCICommon and UE Transmit diversity format 1A specific by (see subclause7.1.2) C-RNTI DCI UE specific by Multi-user MIMO format 1D C-RNTI (seesubclause 7.1.5) Mode 6 DCI Common and Transmit diversity format 1A UEspecific by (see subclause 7.1.2) C-RNTI DCI UE specific by Closed-loopspatial format 1B C-RNTI multiplexing (see subclause 7.1.4) using asingle transmission layer Mode 7 DCI Common and UE If the number of PBCHformat 1A specific by antenna ports is one, C-RNTI Single-antenna port,port 0 is used (see subclause 7.1.1), otherwise Transmit diversity (seesubclause 7.1.2) DCI UE specific by Single-antenna port, format 1 C-RNTIport 5 (see subclause 7.1.1) Mode 8 DCI Common and UE If the number ofPBCH format 1A specific by antenna ports is one, C-RNTI Single-antennaport, port 0 is used (see subclause 7.1.1), otherwise Transmit diversity(see subclause 7.1.2) DCI UE specific by Dual layer transmission, format2B C-RNTI port 7 and 8 (see subclause 7.1.5A) or single-antenna port,port 7 or 8 (see subclause 7.1.1)

<Table 2> above describes supportable DCI format types according to eachtransmission mode in conditions configured by C-RNTI included in 3GPP TS36.213. A terminal performs search and decoding under the assumptionthat the corresponding DCI format exists in a control space sectionaccording to a pre-configured transmission mode. For example, if theterminal receives transmission mode 8 as an indication, the terminalsearches for a DCI format 1A in a common search space and a UE-specificsearch space, and searches for a DCI format 2B only in the UE-specificsearch space.

The wireless communication system has been described with reference tothe LTE system, but the disclosure is not limited to the LTE system, andmay be applied to various wireless communication systems, including NR,5G, and the like. In addition, in an embodiment, in the case of beingapplied to another wireless communication system, the value of kdescribed above may be changed and applied even to a system using amodulation scheme corresponding to FDD.

FIG. 3 is a flowchart illustrating a method for determining an MCS tableby a terminal according to the first embodiment.

A base station may select one of MCS tables, which are designed to havedifferent target block length error rate (BLER) values, and provide theselected MCS table to a terminal (operation 310). For example, one ofthe MCS tables may be an MCS table that is configured with MCS valuessatisfying a target BLER of 10⁻¹ (or a data transmission success rate of90%). This is referred to as a first MCS table in the disclosure.According to another example, one of the MCS tables may be an MCS tableconfigured with MCS values satisfying a target BLER of 10⁻⁵ (or a datatransmission success rate of 99.999%). This is referred to as a secondMCS table in the disclosure.

According to an example, the configuration of the first MCS table may beas shown in <Table 3> below. According to an example, the configurationof the second MCS table may be as shown in <Table 4> below. Referring to<Table 3> and <Table 4>, some MCS indexes may have the same modulationorder, the same target code rate, or the same spectral efficiencyvalues. <Table 3> shows the first MCS table based on the target BLER of10⁻¹, and <Table 4> shows the second MCS table based on the target BLERof 10⁻⁵. In the blank of Table 4, arbitrary values for satisfying thetarget BLER of 10⁻⁵ can be configured. In order to determine amodulation order, a target code rate, and a transport block size (TBS)of a downlink data channel, a terminal identifies MCS index values amongMCS fields, configured as <Table 3> or <Table 4> in downlink controlinformation.

TABLE 3 MCS Index Modulation Target code Rate Spectral I_(MCS) OrderQ_(m) R × [1024] efficiency 0 2 120 0.2344 1 2 157 0.3066 2 2 193 0.37703 2 251 0.4902 4 2 308 0.6016 5 2 379 0.7402 6 2 449 0.8770 7 2 5261.0273 8 2 602 1.1758 9 2 679 1.3262 10 4 340 1.3281 11 4 378 1.4766 124 434 1.6953 13 4 490 1.9141 14 4 553 2.1602 15 4 616 2.4063 16 4 6582.5703 17 6 438 2.5664 18 6 466 2.7305 19 6 517 3.0293 20 6 567 3.322321 6 616 3.6094 22 6 666 3.9023 23 6 719 4.2129 24 6 772 4.5234 25 6 8224.8164 26 6 873 5.1152 27 6 910 5.3320 28 6 948 5.5547 29 2 reserved 304 reserved 31 6 reserved

TABLE 4 MCS Index Modulation Target code Rate Spectral I_(MCS) OrderQ_(m) R × [1024] efficiency 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1718 19 20 21 22 23 24 25 26 27 28 29 30 31

According to the first embodiment, the terminal may determine whether anMCS index indicator in downlink control information (DCI) is based onthe first MCS table or the second MCS table based on one bit in the DCI.In the disclosure, the one bit is described as an MCS table indicator.The MCS index indicator can be configured by five bits in the downlinkcontrol information. For example, if the 1-bit MCS table indicatorindicates “0” (operation 320), the terminal determines a modulationorder and a target code rate of downlink data or uplink data using thefirst MCS table and the index value of the corresponding table(operations 330, 350, and 360). According to another example, if the1-bit MCS table indicator indicates “1” (operation 320), the terminaldetermines a modulation order and a target code rate of downlink data oruplink data using the second MCS table and the index values of thecorresponding table (operations 340, 350, and 360). The 1-bit MCS tableindicator information is included in the downlink control informationexisting together with CRC scrambled by C-RNTI.

For reference, the first MCS table (Table 3) and the second MCS table(Table 4) described in the first embodiment are sufficiently applicableto other embodiments.

According to the (1-1)th embodiment, for a terminal having reported, toa base station, UE capability supporting both a target BLER of 10⁻' anda target BLER of 10⁻⁵, one bit, which is used as an MCS table indicatorin the downlink control information having the CRC scrambled by C-RNTI,may always exist. The MCS table indicator is used to indicate whether anindex value indicated by the MCS index indicator included in thedownlink control information is based on the first MCS table or thesecond MCS table. In the case where the index value is based on thefirst MCS table, the terminal determines a modulation order and a targetcode rate of downlink data or uplink data using the index value based onthe first MCS table. In the case where the index value is based on thesecond MCS table, the terminal determines a modulation order and atarget code rate of downlink data or uplink data using the index valuebased on the second MCS table.

According to the (1-2)th embodiment, for a terminal having reported, toa base station, UE capability supporting only the target BLER of 10⁻¹,the MCS index indicator in the downlink control information existingtogether with CRC scrambled by C-RNTI indicates an index based on thefirst MCS table, and the terminal determines a modulation order and atarget code rate of downlink data or uplink data using the index valuebased on the first MCS table.

According to the (1-3)th embodiment, for a terminal having reported, toa base station, UE capability supporting only the target BLER of 10⁻⁵,the MCS index indicator in the downlink control information having theCRC scrambled by C-RNTI indicates an index based on the second MCStable, and the terminal determines a modulation order and a target coderate of downlink data or uplink data using the index value based on thesecond MCS table.

FIG. 4 is a flowchart illustrating a method for determining an MCS tableby a terminal according to the second embodiment.

According to the second embodiment, the terminal may determine whetheran MCS index indicator in downlink control information is based on afirst MCS table or a second MCS table according to a value indicated byone of the fields existing in the downlink control information(operation 410).

For example, if a new data indicator (NDI) in the downlink controlinformation is toggled, the terminal determines a modulation order and atarget code rate of downlink data or uplink data using an index valueindicated by the MCS index indicator based on the first MCS table. Thismay occur since, in the initial transmission, it is possible to use anMCS table having a high target BLER in order to improve transmissionefficiency.

According to another example, if the NDI in the downlink controlinformation is not toggled, the terminal determines a modulation orderand a target code rate of downlink data or uplink data using an indexvalue indicated by the MCS index indicator based on the second MCStable. This may occur since, in the initial transmission, it is possibleto use an MCS table having a high target BLER in order to increasetransmission efficiency, but in retransmission, the base station mayperform transmission using an MCS table having a lower target BLER valuein order to satisfy the required latency.

For example, if a PDSCH (or PUSCH) mapping type indicates type A in atime resource allocation field in the downlink control information(operation 420), the terminal determines a modulation order and a targetcode rate of downlink data or uplink data using the index valueindicated by the MCS index indicator based on the first MCS table(operations 430, 450, and 460). The PDSCH (or PUSCH) mapping type Arefers to a PDSCH in which the position of a demodulation referencesignal (DMRS) for data decoding is fixed at a specific symbol positionwith reference to a slot boundary regardless of a data transmissionstart symbol position and a data transmission interval size. This isbecause PDSCH (or PUSCH) mapping A is more suitable for eMBBtransmissions requiring a higher target BLER value than URLLC.

According to another example, if the PDSCH (or PUSCH) mapping typeindicates type B in the time resource allocation field in the downlinkcontrol information (operation 420), the terminal determines amodulation order and a target code rate of downlink data or uplink datausing the index value indicated by the MCS index indicator based on thesecond MCS table (operations 430, 450, and 460). In PDSCH (or PUSCH)mapping type B, a DMRS symbol position is changed according to a datatransmission start symbol position and a data transmission intervalsize, and the corresponding DMRS is located at the symbol at which thedata transmission starts. This is because PDSCH (or PUSCH) mapping typeB is more suitable for URLLC transmission requiring a lower target BLERvalue than that required by eMBB.

In addition to the NDI or the PDSCH mapping type illustrated in theabove example, it is sufficiently possible to determine, by theterminal, whether the MCS index indicator is based on the first MCStable or the second MCS table, by replacing the NDI or PDSCH mappingtype with a time resource allocation field, a frequency resourceallocation field, a redundancy version (RV) field, a downlink assignmentindex (DAI) field, a HARQ process number field, a PDSCH-HARQ feedbacktiming indicator field, and the like.

FIG. 5 is a flowchart illustrating a method for determining an MCS tableby a terminal according to the third embodiment.

According to the third embodiment, the terminal may determine whether anMCS index indicator in downlink control information is based on a firstMCS table or a second MCS table, depending on the RNTI type scrambledwith the CRC for the downlink control information (operation 510).

For example, the terminal determines that an MCS index indicator fieldin the downlink control information existing together with the CRCscrambled by RNTI type, such as cell RNTI (C-RNTI), configuredscheduling RNTI (CS-RNTI), system information RNTI (SI-RNTI), pagingRNTI (P-RNTI), or random access RNTI (RA-RNTI), is configured based onthe first MCS table (operations 520 and 530). The terminal determines amodulation order and a target code rate of downlink data or uplink datausing the index value indicated by the MCS index indicator based on thefirst MCS table (operations 530, 550, and 560). The C-RNTI and CS-RNTIare RNTIs used for transmission of information such as eMBB. SI-RNTI isan RNTI used for transmission of system information. P-RNTI is an RNTIused for transmission of paging information. RA-RNTI is an RNTI used fortransmission of random access-related information. The terminaldetermines that the MCS index indicator field in the downlink controlinformation, which exists together with the CRC scrambled by the RNTItype, such as C-RNTI, CS-RNTI, SI-RNTI, P-RNTI, or RA-RNTI, isconfigured based on the first MCS table because uplink data or downlinkdata associated with the RNTIs described above are services that do notrequire a target BLER of 10⁻⁵.

According to another example, the terminal determines that the MCS indexindicator field in the downlink control information, which existstogether with the CRC scrambled by the RNTI type, such as URLLC C-RNTI(U-C-RNTI) or URLLC CS-RNTI (U-CS-RNTI), is configured based on thesecond MCS table (operations 520 and 540). The terminal determines amodulation order and a target code rate of downlink data or uplink datausing the index value indicated by the MCS index indicator based on thesecond MCS table (operations 540, 550, and 560). The U-C-RNTI andU-CS-RNTI are RNTIs used for transmission of information such as URLLC.The terminal determines that the MCS index indicator field in thedownlink control information having the CRC scrambled by the U-C-RNTIand the U-CS-RNTI is configured based on the second MCS table becauseuplink data or downlink data associated with the RNTIs are servicesrequiring a target BLER of 10⁻⁵.

FIG. 6 is a flowchart illustrating a method for determining an MCS tableby a terminal according to the fourth embodiment (610).

According to the fourth embodiment, a terminal may determine whether theMCS index indicator in the downlink control information is based on thefirst MCS table or the second MCS table according to a search space typeof a physical downlink control channel (PDCCH) searched for by theterminal. A set of PDCCH candidates searched for by the terminal iscalled a search space, and a set of PDCCH candidates searched for by allterminals in common is called a common search space (CSS) and a set ofPDCCH candidates individually searched for by a specific terminal iscalled a UE-specific search space (USS).

For example, the terminal determines that the MCS index indicator fieldin the downlink control information found in the common search space isconfigured based on the first MCS table (operations 620 and 630), andthe terminal determines a modulation order and a target code rate ofdownlink data or uplink data using an index value indicated by the MCSindex indicator based on the first MCS table (operations 630, 640, and650). The terminal determines that the MCS index indicator field in thedownlink control information found in the common search space isconfigured based on the first MCS table because the common search spaceis a control information search area used for transmission of data suchas system information, paging information, and random accessinformation, which are not related to a specific data service such aseMBB or URLL, and thus do not require a target BLER of 10⁻⁵.

According to another example, the terminal determines that the MCS indexindicator field in the downlink control information found in theUE-specific search space is configured based on the second MCS table(operations 620 and 640), and the terminal determines a modulation orderand a target code rate of downlink or uplink data using the index valueindicated by the MCS index indicator based on the second MCS table(operations 640, 650, and 660). The terminal determines that the MCSindex indicator field in the downlink control information found in theUE-specific search space is configured based on the second MCS tablebecause the UE-specific search space is a control information searcharea in which data related to a specific data service such as eMBB orURLLC can be transmitted, and a target BLER of 10⁻⁵ is required tosupport data transmission requiring high reliability, such as URLLC. Ifthe terminal determines that the MCS index indicator field in thedownlink control information found in the UE-specific search space isconfigured based on the second MCS table, the terminal that made thedetermination does not correspond to one of terminals supporting onlyeMBB. Instead, the terminal may be one of terminals supporting URLLC.Otherwise, the terminal may not correspond to one of terminals havingreported the capability of URLLC non-supporting to the base station.Instead, the terminal may be one of terminals having reported the UEcapability of URLLC supporting to the base station.

FIG. 7 is a flowchart illustrating a method for determining an MCS tableby a terminal according to the fifth embodiment (710).

According to the fifth embodiment, when the terminal receives, from abase station, configuration of a control resource set (CORESET), whichis a resource area in which downlink control information is searchedfor, the base station may configure whether the MCS index indicatorfield in downlink control information transmitted from the correspondingCORESET is based on the first MCS table or the second MCS table viahigher-layer signaling.

For example, in the case where the base station is configured such thatthe MCS index indicator in the downlink control information transmittedin the first CORESET is based on the first MCS table (operation 720),the terminal determines that the MCS index indicator field found in thefirst CORESET is configured based on the first MCS table (operation730). The terminal determines a modulation order and a target code rateof downlink data or uplink data using the index value indicated by theMCS index indicator based on the first MCS table (operations 750 and760).

According to another example, in the case where the base station isconfigured such that the MCS index indicator in the downlink controlinformation transmitted in the second CORESET is based on the second MCStable (operation 720), the terminal determines that the MCS indexindicator field found in the second CORESET is configured based on thesecond MCS table (operation 740). The terminal determines a modulationorder and a target code rate of downlink data or uplink data using theindex value indicated by the MCS index indicator based on the second MCStable (operations 750 and 760).

FIG. 8 is a flowchart illustrating a method for determining an MCS tableby a terminal according to the sixth embodiment (810).

According to the sixth embodiment, the terminal may determine whether anMCS index indicator in downlink control information is based on thefirst MCS table or the second MCS table according to the downlinkcontrol information format found by the terminal.

For example, the terminal determines that an MCS index indicator fieldin a fallback downlink information format that can be transmitted inboth a common search space and a UE-specific search space is configuredbased on the second MCS table (operations 820 and 840). The terminaldetermines a modulation order and a target code rate of downlink data oruplink data using an index value indicated by the MCS index indicatorbased on the second MCS table (operations 840, 850, and 860). Thefallback downlink control information format may correspond to DCIformat 0_0 for PUSCH scheduling of 5G (NR) and DCI format 1_0 for PDSCHscheduling. The terminal determines that the MCS index indicator fieldin the fallback downlink information format is configured based on thesecond MCS table because the number of fallback downlink informationformat bits is generally smaller than the number of non-fallbackdownlink information format bits, and thus it is suitable for satisfyinga condition (for example, reliability).

According to another example, the terminal determines that the MCS indexindicator field in the non-fallback downlink control information formatthat can be transmitted in the UE-specific search space is configuredbased on the first MCS table (operations 820 and 830). The terminaldetermines a modulation order and a target code rate of downlink data oruplink data using the index value indicated by the MCS index indicatorbased on the first MCS table (operations 830, 850, and 860). Thenon-fallback downlink control information format may correspond to DCIformat 0_1 for PUSCH scheduling of 5G (NR) and DCI format 1_1 for PDSCHscheduling. The terminal determines that the MCS index indicator fieldin the non-fallback downlink information format is configured based onthe first MCS table because the number of non-fallback downlinkinformation format bits is generally larger than the number of fallbackdownlink information format bits, and thus it is not suitable forsatisfying the URLLC requirement (e.g., reliability).

FIG. 9 is a flowchart illustrating a method for determining an MCS tableby a terminal according to the seventh embodiment (910).

According to the seventh embodiment, a terminal may determine whether anMCS index indicator in downlink control information is based on a firstMCS table or a second MCS table according to downlink controlinformation format found by the terminal. In addition, an MCS tableindicator field indicating whether the MCS index indicator is based onthe first MCS table or the second MCS table is separately included in aspecific downlink control information format.

For example, a fallback downlink control information format that can betransmitted in both a common search space and ae UE-specific searchspace includes a 1-bit MCS table indicator field (operation 920). TheMCS table indicator field indicates whether the MCS index indicator isbased on the first MCS table or the second MCS table (operation 940).The terminal determines a modulation order and a target code rate ofdownlink data or uplink data using the index value indicated by the MCSindex indicator based on a specific MCS table indicated by the MCS tableindicator field (operations 942, 944, 960, and 960). The fallbackdownlink control information format may correspond to DCI format 0_0 forPUSCH scheduling of 5G (NR) and DCI format 1_0 for PDSCH scheduling. TheMCS table indicator field is added to the fallback downlink controlinformation format because eMBB and URLLC data can be dynamicallysupported in the fallback downlink control information format at thesame time. In addition, other pieces of information (e.g., systeminformation, paging information, and random access information) otherthan eMBB and URLLC data are also supported in the fallback downlinkcontrol information format.

According to another example, the terminal determines that an MCS indexindicator field in a non-fallback downlink control information formatthat can be transmitted in the UE-specific search space is configuredbased on the first MCS table (operations 920 and 930). The terminaldetermines a modulation order and a target code rate of downlink data oruplink data using the index value indicated by the MCS index indicatorbased on the first MCS table (operations 930, 950, and 960). Thenon-fallback downlink control information format may correspond to DCIformat 0_1 for PUSCH scheduling of 5G (NR) and DCI format 1_1 for PDSCHscheduling. The terminal determines that the MCS index indicator fieldin the non-fallback downlink information format is configured based onthe first MCS table because the number of non-fallback downlinkinformation format bits is generally larger than the number of fallbackdownlink information format bits, and thus it is not suitable forsatisfying the URLLC requirement (e.g., reliability, 10⁻⁵ target BLER).

FIG. 10 is a flowchart illustrating a method for determining an MCStable by a terminal according to the eighth embodiment (1010).

According to the eighth embodiment, a terminal may determine whether anMCS index indicator in downlink control information is based on a firstMCS table or a second MCS table according to a target BLER value relatedto channel quality indicator (CQI) configuration for measurement ofchannel state information (CSI).

A CQI table used for CQI index reporting may include a first CQI tablebased on a target BLER of 10⁻¹ and a second CQI table based on a targetBLER of 10⁻⁵. The base station may configure, via higher-layersignaling, whether the terminal uses the first CQI table or the secondCQI table for CQI index reporting according to the result of channelmeasurement. In addition, CQI index reporting based on a specific CQItable, configured through the higher-layer signaling, can be performedbased on the first CQI table and the second CQI table, which can beindependently configured for a terminal. In other words, the terminalmay receive configuration, as the CQI table used for CQI indexreporting, of the first CQI table, the second CQI table, or both ofthem. The CQI index reporting is transmitted from the terminal to thebase station through an uplink control channel or a data channel.

For example, if the terminal does not receive configuration of the CQIindex reporting based on the second CQI table (operation 1020), theterminal determines that an MCS index indicator field in a downlinkcontrol information format found in a downlink control channel isconfigured based on the first MCS table (operation 1030). The terminaldetermines a modulation order and a target code rate of downlink data oruplink data using the index value indicated by the MCS index indicatorbased on the first MCS table (operations 1030, 1050, and 1060).

When the terminal has received the configuration of the CQI indexreporting based on the second CQI table (operation 1020), the terminaldetermines that the MCS index indicator field in the downlink controlinformation format found in the downlink control channel is configuredbased on the second MCS table (operation 1040). The terminal determinesa modulation order and a target code rate of downlink data or uplinkdata using the index value indicated by the MCS index indicator based onthe second MCS table (operations 1040, 1050, and 1060).

According to the (8-1)th embodiment, if the terminal has received theconfiguration of the CQI index reporting based on the first CQI table,the terminal determines that the MCS index indicator field in thedownlink control information format found in the downlink controlchannel is based on the first MCS table. The terminal determines amodulation order and a target code rate of downlink data or uplink datausing the index value indicated by the MCS index indicator based on thefirst MCS table.

If the terminal has received the configuration of the CQI indexreporting based on the second CQI table, the terminal determines thatthe MCS index indicator field in the downlink control information formatfound in the downlink control channel is configured based on the secondMCS table. The terminal determines a modulation order and a target coderate of downlink data or uplink data using the index value indicated bythe MCS index indicator based on the second MCS table.

If the terminal has received the configuration of all the CQI indexreporting based on both the first CQI table and the second CQI table,the terminal determines that the MCS index indicator field in thedownlink control information format found in the downlink controlchannel is configured based on the second MCS table. The terminaldetermines a modulation order and a target code rate of downlink data oruplink data using the index value indicated by the MCS index indicatorbased on the second MCS table.

According to the (8-2)th embodiment, if the terminal has received theconfiguration of the CQI index reporting based on the first CQI table,the terminal determines that the MCS index indicator field in thedownlink control information format found in the downlink controlchannel is configured based on the first MCS table. The terminaldetermines a modulation order and a target code rate of downlink data oruplink data using the index value indicated by the MCS index indicatorbased on the first MCS table.

If the terminal has received the configuration of the CQI indexreporting based on the second CQI table, the terminal determines thatthe MCS index indicator field in the downlink control information formatfound in the downlink control channel is configured based on the secondMCS table. The terminal determines a modulation order and a target coderate of downlink data or uplink data using the index value indicated bythe MCS index indicator based on the second MCS table.

If the terminal has received the configuration of all the CQI indexreporting based on both the first CQI table and the second CQI table,the downlink control information format found in the downlink controlchannel includes a 1-bit MCS table indicator field. The MCS tableindicator field indicates whether the MCS index indicator is based onthe first MCS table or the second MCS table. The terminal determines amodulation order and a target code rate of downlink data or uplink datausing the index value indicated by the MCS index indicator based on aspecific MCS table indicated by the MCS table indicator field.

According to the (8-3)th embodiment, if the terminal does not receiveconfiguration of the CQI index reporting based on the second CQI table,the terminal determines that the MCS index indicator field in thedownlink control information format found in the downlink controlchannel is configured based on the first MCS table. The terminaldetermines a modulation order and a target code rate of downlink data oruplink data using the index value indicated by the MCS index indicatorbased on the first MCS table.

If the terminal receives the configuration of the CQI index reportingbased on the second CQI table, the 1-bit MCS table indicator is includedin the downlink control information, in a situation in .which specificconditions are satisfied, and the MCS table indicator indicates whetherthe MCS index indicator is based on the first MCS table or the secondMCS table. The terminal determines a modulation order and a target coderate of downlink data or uplink data using the index value indicated bythe MCS index indicator based on a specific MCS table indicated by theMCS table indicator field. The specific conditions are as follows.

-   -   A total of two control information formats existing together        with CRC scrambled by C-RNTI searched for by a terminal.    -   The downlink control information is a DCI format for fallback        (e.g., DCI format 0_0 and DCI format 1_0)    -   The downlink control information is transmitted in a UE-specific        search space.

If at least one of the above conditions is not satisfied, the 1-bit MCStable indicator is not included in the downlink control information, andthe terminal determines whether the MCS index indicator is based on thefirst MCS table or the second MCS table according to the MCStable-related configuration information received via higher-layersignaling. The terminal determines a modulation order and a target coderate of downlink data or uplink data using an index value indicated bythe MCS index indicator based on a specific MCS table configured throughthe higher-layer signaling.

FIG. 11 is a flowchart illustrating a method for determining an MCStable by a terminal according to the ninth embodiment.

According to the ninth embodiment, the terminal determines whether theMCS index indicator in the downlink control information is based on thefirst MCS table or the second MCS table according to a CQI reportingtime point and a valid time (operation 1110).

For example, if there is no resource configured for CQI index reportingbased on the second CQI table, the terminal determines that an MCS indexindicator field in a downlink control information format found in adownlink control channel is configured based on the first MCS table(operations 1120 and 1130). The terminal determines a modulation orderand a target code rate of downlink data or uplink data using the indexvalue indicated by the MCS index indicator based on the first MCS table(operations 1130, 1150, and 1160).

According to another example, if there is a resource configured for CQIindex reporting based on the second CQI table, the terminal determinesthat the MCS index indicator field in the downlink control informationformat, which is searched for in the downlink control channel only for aspecific time period, is configured based on the second MCS table(operations 1120 and 1140). The terminal determines a modulation orderand a target code rate of downlink data or uplink data using the indexvalue indicated by the MCS index indicator based on the second MCS table(operations 1140, 1150, and 1160). Except for the specific time period,the terminal determines that the MCS index indicator field in thedownlink control information format found in the downlink controlchannel is configured based on the first MCS table. The terminaldetermines a modulation order and a target code rate of downlink data oruplink data using the index value indicated by the MCS index indicatorbased on the first MCS table. The specific time period includes a timeperiod k starting from the time point (N) at which the CQI indexreporting is performed based on the second CQI table, for example. Inother words, the specific time period may be a period from N to (N+k).The units of N and k may be slots, symbols, or absolute times.

FIG. 12 is a block diagram illustrating the structure of a terminalaccording to embodiments.

Referring to FIG. 12, a terminal of the disclosure may include aterminal receiver 1200, a terminal transmitter 1204, and a terminalprocessor 1202. The terminal receiver 1200 and the terminal transmitter1204 may be collectively referred to as a transceiver in the embodiment.The transceiver may transmit or receive a signal to or from a basestation. The signal may include control information and data. To thisend, the transceiver may include an RF transmitter for up-converting andamplifying the frequency of the transmitted signal, and an RF receiverfor low-noise amplifying and down-converting the received signal. Inaddition, the transceiver may receive a signal through a wirelesschannel, output the signal to the terminal processor 1202, and transmita signal output from the terminal processor 1202 through the wirelesschannel. The terminal processor 1202 may control a series of processesso that the terminal operates according to the embodiment of thedisclosure described above.

FIG. 13 is a block diagram illustrating the structure of a base stationaccording to embodiments.

Referring to FIG. 13, according to an embodiment, a base station mayinclude at least one of a base station receiver 1301, a base stationtransmitter 1305, and a base station processor 1303. The base stationreceiver 1301 and the base station transmitter 1305 may be collectivelyreferred to as a transceiver in the embodiment of the disclosure. Thetransceiver may transmit or receive a signal to or from the terminal.The signal may include control information and data. To this end, thetransceiver may include an RF transmitter for up-converting andamplifying the frequency of the transmitted signal, and an RF receiverfor low-noise amplifying and down-converting the received signal. Inaddition, the transceiver may receive a signal through a wirelesschannel, output the signal to the base station processor 1303, andtransmit a signal output from the terminal processor 1303 through awireless channel. The base station processor 1303 may control a seriesof processes so that the base station operates according to theembodiment of the disclosure described above.

The embodiments described in the disclosure may not be applicable to UEshaving reported the UE capability of URLLC non-supporting (or 10⁻⁵target BLER non-supporting) to a base station. Alternatively, differentembodiments described in the disclosure may be applicable to UEs havingreported the UE capability of URLLC supporting (or 10⁻⁵ target BLERsupporting) to the base station.

Meanwhile, the embodiments of the disclosure disclosed in thespecification and drawings are merely to provide specific examples inorder to easily explain the technical matters of the disclosure and tohelp understanding of the disclosure, and are not intended to limit thescope of the disclosure. That is, it will be apparent to those skilledin the art that other modified examples based on the technical idea ofthe disclosure may be implemented. In addition, the above embodimentscan be combined with each other and used, as necessary. For example,parts of the first embodiment to the ninth embodiment of the disclosuremay be combined with each other to implement the base station and theterminal. In addition, although the above embodiments have been proposedbased on the NR system, other modified examples based on the technicalidea of the above embodiment may be implemented in other systems, suchas an FDD or TDD LTE system.

In addition, the different embodiments described in the disclosure maybe combined with each other. In addition, the scope of the disclosure isnot limited to the examples described in the disclosure, and theexamples are sufficiently applicable to a sufficiently opposingsituation.

Further, although exemplary embodiments of the disclosure have beendescribed and shown in the specification and the drawings by usingparticular terms, they have been used in a general sense merely toeasily explain the technical contents of the disclosure and helpunderstanding of the disclosure, and are not intended to limit the scopeof the disclosure. It will be apparent to those skilled in the art that,in addition to the embodiments disclosed herein, other variants may beachieved on the basis of the technical idea of the disclosure.

The invention claimed is:
 1. A method performed by a terminal in awireless communication system, the method comprising: transmitting, to abase station, capability information including information on a supportcapability of the terminal associated with a specific target block errorrate (BLER); receiving, from the base station, downlink controlinformation (DCI) scheduling a physical downlink shared channel (PDSCH);identifying that a cyclic redundancy check (CRC) of the DCI is scrambledby a second type radio network temporary identifier (RNTI) associatedwith a second modulation and coding scheme (MCS) table; and in case thatthe CRC of the DCI is scrambled by the second type RNTI associated withthe second MCS table, identifying a modulation order and a target coderate for the PDSCH, based on the second MCS table, wherein the secondtype RNTI is associated with a data with higher reliability.
 2. Themethod of claim 1, further comprising, in case that the CRC of the DCIis scrambled by a first type RNTI associated with a first MCS table,identifying the modulation order and the target code rate for the PDSCHbased on the first MCS table associated with the first type RNTI,wherein the first type RNTI is a cell-RNTI (C-RNTI).
 3. The method ofclaim 1, further comprising: receiving, from the base station, a messageconfiguring a channel quality indicator (CQI) table associated with thespecific target BLER of 10Λ−5, by a higher layer signaling.
 4. Themethod of claim 1, wherein the terminal monitors the DCI based on both afirst type RNTI and the second type RNTI.
 5. The method of claim 1,further comprising: receiving, from the base station, DCI scheduling aphysical uplink shared channel (PUSCH); identifying that a CRC of theDCI is scrambled by the second type RNTI associated with the second MCStable; and in case that the CRC of the DCI is scrambled by the secondtype RNTI associated with the second MCS table, identifying a modulationorder and a target code rate for the PUSCH based on the second MCStable.
 6. A method performed by a base station in a wirelesscommunication system, the method comprising: receiving, from a terminal,capability information including information on a support capability ofthe terminal associated with a specific target block error rate (BLER);generating downlink control information (DCI) scheduling a physicaldownlink shared channel (PDSCH), a cyclic redundancy check (CRC) of theDCI being scrambled by a second type radio network temporary identifier(RNTI); and transmitting, to the terminal, the DCI, wherein the secondtype RNTI is associated with a second modulation and coding scheme (MCS)table, wherein the second type RNTI is associated with a data withhigher reliability, and wherein, in case that the CRC of the DCI isscrambled by the second type RNTI associated with the second MCS table,a modulation order and a target code rate for the PDSCH are identifiedbased on the second MCS table.
 7. The method of claim 6, wherein, incase that the CRC of the DCI is scrambled by a first type RNTIassociated with a first MCS table, the modulation order and the targetcode rate for the PDSCH are identified based on the first MCS tableassociated with the first type RNTI, and wherein the first type RNTI isa cell-RNTI (C-RNTI).
 8. The method of claim 6, further comprising:transmitting, to the terminal, a message configuring a channel qualityindicator (CQI) table associated with the specific target BLER of 10Λ−5,by a higher layer signaling.
 9. The method of claim 6, furthercomprising: transmitting, to the terminal, DCI scheduling a physicaluplink shared channel (PUSCH), wherein, in case that the CRC of the DCIis scrambled by the second type RNTI associated with the second MCStable, a modulation order and a target code rate for the PUSCH areidentified based on the second MCS table.
 10. A terminal in a wirelesscommunication system, the terminal comprising: a transceiver configuredto transmit and receive a signal; and a controller coupled with thetransceiver and configured to: transmit, to a base station, capabilityinformation including information on a support capability of theterminal associated with a specific target block error rate (BLER),receive, from the base station, downlink control information (DCI)scheduling a physical downlink shared channel (PDSCH), identify that acyclic redundancy check (CRC) of the DCI is scrambled by a second typeradio network temporary identifier (RNTI) associated with a secondmodulation and coding scheme (MCS) table, and in case that the CRC ofthe DCI is scrambled by the second type RNTI associated with the secondMCS table, identify a modulation order and a target code rate for thePDSCH based on the second MCS table, and wherein the second type RNTI isassociated with a data with higher reliability.
 11. The terminal ofclaim 10, wherein, in case that the CRC of the DCI is scrambled by afirst type RNTI associated with a first MCS table, the modulation orderand the target code rate for the PDSCH are identified based on the firstMCS table associated with the first type RNTI, and wherein the firsttype RNTI is a cell-RNTI (C-RNTI).
 12. The terminal of claim 10, whereinthe controller is further configured to receive, from the base station,a message configuring a channel quality indicator (CQI) table associatedwith the specific target BLER of 10Λ−5, by a higher layer signaling. 13.The terminal of claim 10, wherein the terminal monitors the DCI based onboth a first type RNTI and the second type RNTI.
 14. The terminal ofclaim 10, wherein the controller is further configured to: receive, fromthe base station, DCI scheduling a physical uplink shared channel(PUSCH); identify that a CRC of the DCI is scrambled by the second typeRNTI associated with the second MCS table; and in case that the CRC ofthe DCI is scrambled by the second type RNTI associated with the secondMCS table, identify a modulation order and a target code rate for thePUSCH based on the second MCS table.
 15. A base station in a wirelesscommunication system, the base station comprising: a transceiverconfigured to transmit and receive a signal; and a controller coupledwith the transceiver and configured to: receive, from a terminal,capability information including information on a support capability ofthe terminal associated with a specific target block error rate (BLER),generate downlink control information (DCI) scheduling a physicaldownlink shared channel (PDSCH), a cyclic redundancy check (CRC) of theDCI being scrambled by a second type radio network temporary identifier(RNTI), and transmit, to the terminal, the DCI, wherein the second typeRNTI is associated with a second modulation and coding scheme (MCS)table, wherein the second type RNTI is associated with a data withhigher reliability, and wherein, in case that the CRC of the DCI isscrambled by the second type RNTI associated with the second MCS table,a modulation order and a target code rate for the PDSCH are identifiedbased on the second MCS table.
 16. The base station of claim 15,wherein, in case that the CRC of the DCI is scrambled by a first typeRNTI associated with a first MCS table, the modulation order and thetarget code rate for the PDSCH are identified based on the first MCStable associated with the first type RNTI, and wherein the first typeRNTI is a cell-RNTI (C-RNTI).
 17. The base station of claim 15, whereinthe controller is further configured to transmit, to the terminal, amessage configuring a channel quality indicator (CQI) table associatedwith the specific target BLER of 10Λ−5, by a higher layer signaling. 18.The base station of claim 15, wherein the controller is furtherconfigured to transmit, to the terminal, DCI scheduling a physicaluplink shared channel (PUSCH), and wherein, in case that the CRC of theDCI is scrambled by the second type RNTI associated with the second MCStable, a modulation order and a target code rate for the PUSCH areidentified based on the second MCS table.